Render only has gray textures
You have a material override set in your Scene>Layer panel. (Where it says 'Material'). Hit the cross in there to deactivate it.



EDIT:

Newer versions of blender don't use layers, but "collections" so the override function is in the scene>View Layer section.



Additional info:

Where is the Layers panel in Blender 2.8?

2.8 - Is it possible to assign (override) a material to a whole collection?